title: Architecture of the RNA polymerase-Spt4/5 complex and basis of universal transcription processivity.
abstract: Related RNA polymerases (RNAPs) carry out cellular gene transcription in all three kingdoms of life. The universal conservation of the transcription machinery extends to a single RNAP-associated factor, Spt5 (or NusG in bacteria), which renders RNAP processive and may have arisen early to permit evolution of long genes. Spt5 associates with Spt4 to form the Spt4/5 heterodimer. Here, we present the crystal structure of archaeal Spt4/5 bound to the RNAP clamp domain, which forms one side of the RNAP active centre cleft. The structure revealed a conserved Spt5-RNAP interface and enabled modelling of complexes of Spt4/5 counterparts with RNAPs from all kingdoms of life, and of the complete yeast RNAP II elongation complex with bound Spt4/5. The N-terminal NGN domain of Spt5/NusG closes the RNAP active centre cleft to lock nucleic acids and render the elongation complex stable and processive. The C-terminal KOW1 domain is mobile, but its location is restricted to a region between the RNAP clamp and wall above the RNA exit tunnel, where it may interact with RNA and/or other factors.
authors.affiliation: Gene Center and Department of Biochemistry, Center for Integrated Protein Science Munich (CIPSM), Ludwig-Maximilians-Universität München, Munich, Germany.
authors.forename: Fuensanta W
authors.initials: FW
authors.lastname: Martinez-Rucobo
authors.forename: Sarah
authors.initials: S
authors.lastname: Sainsbury
authors.forename: Alan C M
authors.initials: AC
authors.lastname: Cheung
authors.forename: Patrick
authors.initials: P
authors.lastname: Cramer
mesh_terms: D000595:Amino Acid Sequence; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry*; D018360:Crystallography, X-Ray; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D020027:Pyrococcus furiosus / Q000737:chemistry* / Q000201:enzymology*; D012097:Repressor Proteins / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000201:enzymology; D017386:Sequence Homology, Amino Acid; D035602:Transcriptional Elongation Factors / Q000737:chemistry*
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D012097:Repressor Proteins; D035602:Transcriptional Elongation Factors; C069940:SPT5 transcriptional elongation factor; D012321:DNA-Directed RNA Polymerases